1. Field of the Invention
The present invention relates to a printer for performing recording on a sheet material and a printing method. In particular, the invention relates to a printer used for a sheet material having a recording surface (printing surface) on which recording such as printing is performed and a heat-sensitive adhesive surface that is formed on an opposite side of the recording surface and develops an adhesive force upon heating.
2. Description of the Related Art
Up to now, there is known an apparatus used as a printer for performing recording on a sheet material having a recording surface on one side and a heat-sensitive adhesive surface on the other side, as disclosed in JP 2003-316265 A (see FIG. 1).
The printer includes: a printing unit having a printing thermal head for performing printing on a recording surface of a sheet material; a cutter unit, arranged downstream of the printing unit, for cutting the sheet material to a predetermined length; and a thermal activation unit, arranged downstream of the cutter unit, having a thermally-activating thermal head for performing thermal activation on a heat-sensitive adhesive surface on the opposite side of the recording surface of the sheet material. Further, the printing unit and the thermal activation unit each include: a platen roller for conveying the sheet material while pressing it against a heat generating portion of the thermal head; a motor for rotating and driving the platen roller; and other components, as conveyance means for the sheet material.
In the printer as constructed above, while the sheet material is conveyed by the platen roller of the printing unit, the printing thermal head of the printing unit performs printing on the recording surface of the sheet material. After that, the cutting unit cuts the recorded sheet material to a predetermined length. Then, while one sheet of the recorded sheet material is conveyed by the platen roller of the thermal activation unit, the heat-sensitive adhesive surface on the opposite side of the recording surface of the sheet material is heated by the thermally-activating thermal head of the thermal activation unit. As a result, an adhesive force of the heat-sensitive adhesive surface develops, and the one sheet of the recorded sheet material can be directly affixed to a corrugated board, a food wrap, a glass bottle, a plastic container, etc.
Currently, miniaturization and lightness are increasingly demanded for a printer handling the above-mentioned sheet material in order that the printer is used as a mobile printer a person easily carries with one hand.
However, in the printer disclosed in JP 2003-316265 A, the printing unit and the thermal activation unit are separately constructed. Thus, a thermal head, a platen roller for conveying a sheet material, a motor, and the like must be provided in each of the printing unit and the thermal activation unit.
For this reason, the printer construction disclosed in JP 2003-316265 A has a limitation in achieving further lightness and miniaturization.
To solve the problem, there is a conventional thermal printer having a single thermal head arranged on a platen roller, and printing and thermal activation are selectively performed with the thermal head. In this printer, after printing is performed on a surface (printing surface) of a heat-sensitive adhesive sheet, the surface of the heat-sensitive adhesive sheet is reversed by a reversing roller. Then, the reversed heat-sensitive adhesive sheet is inserted again from a discharge side of the thermal head and thermal activation is performed on its rear surface (heat-sensitive adhesive surface).
However, the printer additionally needs the reversing roller, and there is a problem in that miniaturization of the apparatus is hindered.
In general, as shown in FIG. 9, a thermal printer adopts such a construction that a part of a heat generating portion 21a of a thermal head 21 is in press contact with an outer circumferential surface of a platen roller 22. Also, to miniaturize the head, in the thermal head 21, the heat generating portion 21a is arranged in the vicinity of one end portion 21b of the head. For this reason, regarding a distance between a thermal head substrate and the platen roller outer circumferential surface at portions other than the press contact part, the distance is extremely small on the end portion 21b side where the heat generating portion 21a is arranged than at an end portion 21c on the opposite side of the end portion 21b. Accordingly, it is difficult to insert a recording sheet from the end portion 21b side where the heat generating portion 21a is arranged.
Note that, to attain a construction allowing a sheet to be inserted from the end portion 21b side, a distance from the heat generating portion 21a to the end portion 21b may be set longer. However, if the distance is set longer in this way, the thermal head size becomes large, which leads to increase in costs.